The present invention relates to improvements in the processes for radiotelegraphic or telephonic communications in which a primary station Whose emanations are received 3 by a secondary station, may, in turn, receive from the latter, being thus able to secure a junction, although there is no energy supply at the secondary station,

The primary station comprises a source of oscillations and an emitting circuit; the secondary has a receiving circuit with no local energy source, and in which is inserted a manipulating or modulating device (telephonic or telegraphic apparatus).

At the primary station, the receiving circuit is connected, directly or inductively, to the emitting circuit, and the ordinary amplifying devices are used. Of course, the communicating stations must be tuned; this tuning is obtained in the well-known means.

In the drawing is illustrated as an example a diagrammatic arrangement embodying the invention and giving the best results.

At the secondary station R, is provided an aerial 7 with tuning condenser 8, constituting a circuit tuned to the waves emitted by the primary station.

When the circuit E works as an emitting one, and assuming that the stations E and R are tuned, if one manipulates, by making a cut 9, in the circuit R, the effect of this manipulation will be received on the circuit E. Further, if a transformer 7--8, with am plifying device 9, is COIlDGC'EGCl'WllCh the emitu' ting circuit Q-3l513-612, the signals of the circuit R will be received the telephone 11, at the outlet of the amplifying device.

Moreover, these signals may be produced by a telephonic modulation as Well as a telegraphic one, according to whether a microphone or key is used.

Having described my lnventron, what I claim is 1. A system of radio communication comprising a main transmitting station, an oscillator tube and transmitting aerial therefor at the main station, means for adjusting the frequency of the oscillator, means for tuning the transmitting aerial, a secondary station Without energy source having an aerial arranged to be tuned to the frequency of the transmitting aerial of the main station, means wholly at the secondary station for modulating the electrical energy induced in its aerial according to a signal to be transmitted to the main station, and an amplifying receiver at the main station operatively connected with the oscillator tube and its transmitting aerial for receiving the modulations produced at the secondary station.

2. A system of radio communication comprising a main station, a secondary station, a tuned circuit at the secondary station without energy source, means for varying the electrical condition of said tuned circuit, and unitary means at the primary station for transmitting unmodulated radio waves to the tuned circuit at the secondary station and responsive to the variations in the electrical condition of said tuned circuit to render the same perceptible at the primary station.

3. A system of radio communication comprising an audion tube oscillator and circuit therefor having a plate-filament circuit and a grid-filament circuit, an antenna connected With the plate circuit and a radio receiving set connected with the grid circuit, a remote non-generating circuit arranged to receive waves radiated from said antenna, and means for modulating the Waves in said non gencrating circuit, said antenna and non-generating circuit being so related that the modulated Waves will in effect be transmitted to the said antenna, and said radio receiving set being arranged to respond to said modulations, substantially the entire energy of all of said Waves being derived from a common source.

4. The method of radio communication which consists in transmitting radio waves of a length above ten meters from a primary station to a resonant circuit without energy source at a secondary station, modulating said Waves in circuit at the secondary station with signal modulations, and transmitting the modulated Waves from the secondary station to the primary station Without additional energy.

5. The method of radio signaling which comprises generating radio frequency Wave energy at one station, transmitting the same to a second station, transforming the Wave energy received at the second station Without additional energy into current oscillations, modulating said current oscillations at the second station to produce modulated Wave energy, and receiving and demodulating the modulated Wave energy at a point remote from the second station.-

6. The method of radio signaling which comprises generating radio frequency Wave energy at one station, transmitting the same to a resonant circuit Without energy source at a second station, modulating the wave energy received thereat, receiving said modulated ave energy through space at a, point remote from said second station, and detecting the modulations from said received modulated Wave energy.